Shortcomings in cancer care disproportionately affect minority group members and contribute to racial and ethnic disparities in cancer mortality. Many of the nearly 15 million US adults insured by Medicaid are Black or Hispanic and therefore, evaluating cancer care delivery in the context of these state health insurance programs is a logical strategy to identify the sources of disparities. By merging Medicaid enrollment and claims files with tumor registry data from New York and California, 2 states with large ethnically diverse populations and many Medicaid enrollees, we seek to identify how access to safety net health insurance and race/ethnicity intersect with common cancer diagnoses. The overarching questions we will address are: Where are there opportunities for decreasing the cancer burden for the poor? Does cancer care delivery in Medicaid achieve reasonable quality benchmarks? Do racial disparities in treatment persist within Medicaid? Specifically, we will evaluate aspects of care we understand well based on our team's prior work using Medicare-registry linked data: 1) Stage distribution at diagnosis, a marker for cancer severity and access to medical care; 2) Cancer surgery and the receipt of complex operations at experienced hospitals with high procedure volume; and, 3) Adjuvant radiation and chemotherapy treatments for cancers where these interventions improve outcomes. Analyses will focus on common solid tumors among two groups of Medicaid enrollees: adults aged 21-64 and the elderly aged 65+ dually enrolled in Medicare. We will evaluate care patterns for Medicaid patients and where data permit, compare them to patterns for otherwise similar persons not covered by Medicaid. Specifically, for each important aspect of cancer care we will also measure racial/ethnic disparities within the Medicaid program and test our hypothesis that they are minimized for patients with long term enrollment prior to diagnosis. More generally, this project will construct a resource for health services researchers, characterize its yield, and use it to identify and prioritize specific opportunities to improve cancer care delivery for vulnerable Americans. PUBLIC HEALTH RELEVANCE: Cancer care is not as good as it should be for all Americans. It is well known that care is sub-optimal for persons who are poor, many of whom are insured by State Medicaid programs. This study asks the question, is cancer care as good as it should be for patients who receive their health insurance from state Medicaid programs? Do patients who have long term access to Medicaid present with more advanced stage disease? Do they receive necessary treatments? Do the gaps in care on the basis of race and ethnicity exist within the Medicaid program? Is the information recorded on Medicaid claims reliable enough to identify important aspects of cancer treatment like surgery, radiation and chemotherapy? Could linkage of Medicaid enrollment and/or claims data to cancer registry data provide a framework for ongoing monitoring of quality of care? By examining data from New York and California which have large multiethnic populations and many persons living in poverty, this study will answer these questions and identify opportunities to improve cancer care delivery to poor Americans.